How do I get past (level 6)?

Don't try to shoot at the open tube in the center.

After you blow off his arms he will roar then shoot 5 projectiles out of his mouth at you. Use kinesis to grab the first projectile and smash the second with it, use kinesis again to grab the third projectile and smash the fourth with it, then grab the fifth projectile and throw it back in his mouth. Repeat this a few times and he's finished. Once you get the rhythm of this boss fight he's pretty easy.

The only problem you might run into is that sometimes his remaining arms will block some of the projectiles and throw off the count. Try to maneuver around the room so when the projectile comes out it wont hit an arm. If one does get smashed into his arm try to get another to hit his arm or shoot however many you need to shoot so you can freely throw the last projectile.